1. Field of the Invention
This invention is related to the field of fuel-fired steam generators. More particularly, this invention refers to a means to provide multiple ignition of individual pilot lights associated with a multiplicity of individual boiler tube assemblies contained within a housing.
2. Description of the Prior Art
U.S. Pat. No. 3,695,811 describes a pilot and main fuel gas supply means for pressurized gas-fired space heaters or the like. This invention describes a means for supplying pilot and main fuel gas to the fuel gas-combustion air mixing area of a gas-fired heater which employs pressurized combustion means. The pressurized combustion means include an elongate trough having an imperforate base wall and long side walls that are pierced by a plurality of pressurized combustion air inlet apertures and a fuel gas supply conduit which extends generally longitudinally through the trough. The fuel gas supply conduit has a long surface that is pierced by a plurality of apertures through which fuel gas can enter the trough and be turbulently mixed with pressurized combustion air in a fuel-gas-air mixture area defined by the apertured trough side walls and the apertured fuel-gas supply conduit surface, and can be ignited therein to produce an intense flame. The invention describes a pilot and a main fuel gas supply means by installing a partition means which divide the hollow fuel supply conduit into a pilot and a main gas supply portion. Ignition means is provided for the pilot fuel supply source to ignite the pilot fuel thus providing a source of heat for main fuel that is bled through the elongated surrounding tube into the main combustion area. This invention differs from the instant invention in that the pilot fuel and ignition source serves to ignite main fuel in a single combustion chamber.
The present invention provides a single source of ignition for a multiplicity of individual combustion devices thus providing combustion wave ignition for each of the combustors.
Additionally, the present invention differs from the foregoing prior art patent in that a separate source of pilot fuel is supplied adjacent the injector of each combustion device, thus providing a local pilot flame for each combustor that is ignited from a combustion wave from a singular hot gas generator plenum chamber.
U.S. Pat. No. 3,751,210 entitled, "Two-Stage Vaporizing Fuel Oil Burner," assigned to the assignee of the present invention, describes a system similar to the foregoing prior art patent wherein the invention describes a device which achieves vaporization of liquid fuel, such as fuel oil in a "free stream" by burning a small percentage of the fuel on the fringes of a spray of atomized droplets. A small pilot flame is maintained within a housing and is supplied by one of a pair of atomizers to vaporize fuel being injected into the same housing from the second atomizer. The heated chamber within the housing thus vaporizes all the fuel. Both atomizers induce sufficient air through aspiration ports in the housing to premix fuel and air. The fuel ejected from the pilot atomizer experiences a reduction of droplet size through use of a long cone-shaped device which deflects and collects a portion of fuel spray. Gaseous fuel is subsequently burned in a primary combustion chamber downstream of the vaporizing housing. The main difference between U.S. Pat. No. 3,751,210 and U.S. Pat. No. 3,695,811 is that the U.S. Pat. No. 3,751,210 patent preheats a housing which vaporizes through the use of a pilot flame fuel injected into the same housing, the vaporized fuel being subsequently ignited downstream of the vaporizing chamber. The U.S. Pat. No. 3,695,811 patent provides a pilot source by dividing fuel between a main supply source and the pilot fuel supply source. The ignited pilot fuel subsequently ignites the gaseous fuel entering a main combustion chamber through a series of apertures in the main fuel supply source.
The instant invention differs from both of the prior art inventions in that a pilot combustion plenum chamber is provided that consists of a multiplicity of conduits communicating between the pilot combustion plenum and individual combustors in a steam generator device or the like. A combustion wave heat source generated in the combustion plenum chamber propagates down each conduit between the plenum chamber and the individual combustion chambers igniting the pilot fuel therein, thus providing a pilot flame for ignition of fuel and oxidizer that is independently fed to each of the combustors in a multi-combustor device.
The present invention provides a means to ignite a multiplicity of combustors arrayed in a housing, each combustor device is an individual source of heat to convert water to superheated steam, thereby providing many small steam generators for use in driving steam turbines, or the like. The main problem is to provide a source of ignition to simultaneously light each pilot associated with the several combustors in the steam generator apparatus.
As background information, a copending patent application entitled, "Compact High-Pressure Steam Generator," is comprised of a multiplicity of individual burner tube assemblies, each boiler tube is comprised of concentric tubes. The inner tube being essentially a fire tube wherein gaseous fuel and gaseous oxidizer are ignited and combusted, the heat generated thereby radiating through the inner fire tube into an annular chamber formed by the inner fire tube and the outer concentric tube. Water is circulated through the chamber defined by the tube, the water being converted to superheated steam as it exits the opposite end of the tube from the injector. The compact steam generator is comprised of a multiplicity of individual boiler tube units and the problem, as stated heretofore, is to ignite the oxygen and the fuel in each of the fire tubes simultaneously to start the steam generating process. Each injector at one end of the individual boiler tube assemblies has an individual source of pilot fuel such as propane. In order to ignite the pilot fuel adjacent each injector, a source of ignition must be provided to the exit end of the pilot tube. A hot gas generator plenum chamber is provided which is supplied with a source of fuel and a source of oxidizer. The plenum chamber has individual conduits communicating between the plenum chamber and each of the injectors of the boiler tube assemblies. Upon ignition of the fuel and oxidizer in the plenum chamber a hot gas combustion wave is generated and the wave propagates down each of the individual tubes adjacent to the injectors of the boiler tube assemblies, providing a source of ignition to ignite the pilot fuel exiting the end of each of the pilot fuel tubes. After ignition of the pilot fuel adjacent each injector, the hot gas generator plenum chamber providing the initial combustion wave is converted to a main fuel plenum chamber. Each conduit between the plenum chamber and the injector then becomes a main fuel supply source that is subsequently mixed with an oxidizer independently supplied to each of the injectors of each of the multiplicity of fire tube assemblies. The fuel from the plenum chamber and the oxidizer supplied from a separate source then is ignited by the pilot flame previously ignited by the combustion wave from the plenum chamber. After mainstage ignition of each of the individual boiler tube assemblies, the source of pilot fuel can then be shut down, the main stage combustion being self-sustaining.
Therefore, it is an object of this invention to provide a source of ignition for a multiplicity of individual injectors associated with a steam generator or the like.
More specifically, it is an object of this invention to provide a source of ignition to ignite individual pilots that are placed adjacent to separate injectors associated with a multiplicity of boiler tube assemblies to ignite a pilot in each individual injector. The conduit supplying the intitial combustion wave to ignite each pilot adjacent each injector then becomes a conduit to supply the main fuel source to each injector.
An advantage over the prior art ignitor means is the ignition of pilot light fuel in several individual main combustion chambers by utilizing a combustion wave which is generated from a source remote from the pilot fuel source.
Another advantage over the prior art is the ability to utilize a common plenum chamber as a hot gas generator and as a means to provide main fuel or oxidizer to several combustion devices.
Yet another advantage is the ability to ignite simultaneously a multiplicity of pilots associated with individual combustor devices.
The above noted objects and advantages of the present invention will be more fully understood upon a study of the following detailed description in conjunction with the detailed drawing.